It has typically been known that an exhaust gas emission control system is provided in an exhaust pipe of an engine and the like to collect particulate matters (PM) (i.e., particulate substances) contained in exhaust gas which cause black exhaust, thereby preventing discharge of the PM into the atmosphere (see, for instance, Patent Literature 1).
The exhaust gas emission control system of Patent Literature 1 includes an inlet unit, a processing unit that houses a filter for capturing PM in exhaust gas, and an outlet unit, each of the units being formed in a cylindrical shape. The inlet unit and the outlet unit are respectively connected to ends of the processing unit.
The inlet unit includes: an inlet pipe that is connected to an exhaust pipe from an engine; and a first main body pipe that is connected to the end of the processing unit and houses a flow regulation member formed in a meshed pattern. The inlet pipe is connected to a cut portion provided on an outer surface of the first main body pipe in a manner to radially project. With this arrangement, after exhaust gas flowing into the first main body pipe from the inlet pipe of the inlet unit is regulated by the flow regulation member of the first main body pipe, the exhaust gas is purified by the filter inside the processing unit and flows out of the outlet unit.